Electrical activation of central and peripheral nervous system has been investigated for treatment of neural disorders for many decades and a number of devices have already moved into clinical phase with success. As we learn more about the neural circuitry in the spinal cord and the brain, new applications are targeting more specific circuits in the central nervous system and thus requiring much more localized means of electrical stimulation. Some example neural prosthetic applications are microstimulation of the spinal cord to restore locomotion or micturition in spinal cord injury, microstimulation of the cochlear nucleus, midbrain, or auditory cortex to restore hearing, and stimulation of the visual cortex in the blind subjects. In order to satisfy the demand in these applications, microelectrode arrays have been developed over the past decade. However, the current implantable microelectrode arrays use wired interconnects for applying the electric stimulations. These fine wires are a major source of device failure since they are the first to break in chronic implants. Moreover, the brain and the spinal cord experience significant amounts of translation inside the skull and the spinal column. Movement of the tissue around these rigid microelectrodes causes significant shear forces due to the mechanical mismatch between the electrode material and the neural tissue. These shear forces, exacerbated by the tethering forces of the wired interconnects, result in a thick encapsulation tissue layer that forms around the electrode. The mechanical mismatch and tethering forces not only cause cellular damage but also the loss of specificity of the stimulations because of this barrier that forms between the electrode and the targeted neurons. We propose a floating micro-electrical device as an alternative technology to micro-electrode arrays. The proposed micro-stimulators will be energized with an infrared light beam through an optical fiber located just outside the dura mater. The floating microstimulators will be free from any interconnects and tethering forces. Because the overall device size is much smaller, the insult to the neural tissue will also be much reduced. The main objective of this proposal is to develop and characterize these floating light activated micro-electrical stimulators (FLAMES). This technology can be instrumental in translation of many neural prosthetic approaches into the clinic, particularly those that involve microstimulation of the spinal cord. PUBLIC HEALTH RELEVANCE: The main objective of this proposal is to develop and test wireless microstimulators (<300 micron) for electrical activation of the central nervous system in neural prosthetic applications, such as those developed for individuals with spinal cord injury to regain some vital functions. We believe that these wireless micro-stimulators will eliminate the problems encountered with current microelectrode technology and thus enable the transfer of many neural prosthetic projects into the clinic.